Apparatus for holding and guiding an elongated electrode in electro-erosion machining

ABSTRACT

A holder for supporting and guiding an elongated and relatively slender electrode in an electro-erosion apparatus, for example for drilling holes of a very small diameter in a workpiece. The holder comprises essentially a straight edge surface against which the elongated slender electrode is applied by fluid pressure. The fluid pressure may be the atmospheric pressure, conduit means being provided proximate the straight edge surface for exhausting atmospheric air by connection to a suction means, or the fluid may be any other fluid under pressure for exerting a force on one side of the electrode to apply it against the straight edge surface.

United States Patent [191 Girardin 5] Jan. 16, 1973 APPARATUS FORHOLDING AND [56] References Cited GUIDING AN ELONGATED N P N ELECTRODEIN ELECTRO-EROSION U [TED STATES ATE Ts MACHINING 3,517,153 6/1970 Check..2l9/69 s Inventor: Roger Girardin, Lausanne, Switzerland Assignee:Ateliers des Charmilles, S.A.,

Geneva, Switzerland Filed: March 27, 1972 Appi. No.: 238,229

Foreign Application Priority Data March 3], I97] Switzerland ..4680/7lU.S. Cl. ..2l9/69 E, 219/138 Int. Cl. ..B23k 1/08 Field of Search..2l9/69 E, 138-144 Primary Examiner-R. F. Staubly AttorneyRobert C.Haukeet al.

[ ABSTRACT A holder for supporting and guiding an elongated andrelatively slender electrode in an electro-erosion apparatus, forexample for drilling holes of a very small diameter in a workpiece. Theholder comprises essentially a straight edge surface against which theelongated slender electrode is applied by fluid pressure. The fluidpressure may be the atmospheric pressure, conduit means being providedproximate the straight edge surface for exhausting atmospheric air byconnection to a suction means, or the fluid may be any other fluid underpressure for exerting a force on one side of the electrode to apply itagainst the straight edge surface.

9 Claims, 7 Drawing Figures PATENTEDJAH 16 1915 SHEET 1 nr 2 FIGI FIG. 2

PATENTEDJAN 16 1975 3,711,675

sum 2 0F 2 F|G.5 FIG.4

FIG.6 FIG APPARATUS FOR HOLDING AND GUIDING AN ELONGATED ELECTRODE INELECTRO- EROSION MACHINING BACKGROUND OF THE INVENTION Electro-erosionapparatus, more particularly electrical discharge machining apparatus,are advantageously used for some machining operations such as, forexample, for drilling very small holes in a conductive workpiece. Whendrilling such small diameter holes, of the order of a few hundredths ofa millimeter, the electrode consists of a slender conductive wire, forexample made of copper, aluminum or tungsten. When the electrode wirehas a very small diameter for example a diameter of a one hundredth orless of a millimeter, holding the electrode wire in an accurate positionon an appropriate holder is a very delicate and complex proposition.

The present invention provides several means for securedly and preciselyholding an electrode wire having a relatively small diameter whichremedies the difficulties presented by prior art electrode wire holders,although it will be obvious to those skilled in the art that theinvention can be used with advantage for holding any other elongatedrelatively slender electrode in electro-erosion machining apparatus.

SUMMARY a fluid exerting a pressure urging the electrode against thestraight edge surface.

The objects and advantages of the invention will become apparent whenthe following description of the best modes contemplated for practicingthe invention is read in conjunction with the accompanying drawingswherein:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic perspective viewof an electrode holder according to the present invention;

FIG. 2 is a transverse sectional view along plane 2-2 of'FIG. 1;

FIG. 3 is a transverse sectional view along plane 3-3 of FIG. 1;

FIG. 4 is a view similar to FIG. 3 but showing a modification of theinvention;

FIG. 5 is a view similar to FIG. 4 but showing a further modification ofthe invention;

FIG. 6 is a view similar to FIG. 5 but showing a further modificationofthe invention; and

FIG. 7 is a view similar to FIG. 6 but showing an additionalmodification of the invention.

DETAILED DESCRIPTION OFTHE PREFERRED EMBODIMENT Referring now to FIGS. 1and 3, an electrode holder according to the invention comprises anelongated block or support member 10 having a planar face 12 on which isaffixed a pair of symmetrically disposed guide members 14 and 16fastened to the support member 10 by way of screws 18. In the example ofstructure shown at FIGS. 1 and 3, the juxtaposed sides of the guidemembers 14 and 16 form a pair of converging planar straight edgesurfaces, respectively shown at 20 and 22, which are disposed at anangle so as to define a V- shaped channel for an electrode wire 24disposed at the bottom of the channel. The electrode wire is held at thebottom of the V-shaped channel by atmospheric pres sure, as a result ofa suction being exerted at the bottom of the channel by means of one orseveral conduits 26 placing the apex or bottom of the V-shaped channelwith a common manifold 28 connected to a suction means, such as a vacuumpump, not shown, by a pipe 30.

As shown at FIGS. 1 and 2, the guide members 14 and 16 may be modifiedon a portion of their length to function as a pair of supports 14a and16a for a pair of opposed jaw members 32 and 34 for laterally clampingthe electrode wire 24 for feeding the wire longitudinally relatively tothe guide members 14 and 16. The jaw member 32 is laterally movablerelative to the support 14a by being supported and guided therefrom bymeans of a guiding and mounting bolt 33 transversely disposedtherethrough, and the right hand end thereof is urged toward the wireelectrode 24 by means such as spring 37. The jaw member 34 is laterallydisplaceable by means of a piston 38 operated by fluid pressureintroduced and exhausted from a cylinder 39 formed in the support 1611,a return spring 41 causing the piston 38 and consequently the jaw member34 to be displaced rightwardly by the return spring when fluid isexhausted from the cylinder 39. The wire electrode 24 is thus clampedand unclamped between the two jaw members 32 and 34 according to whetheror not fluid is introduced in the cylinder 39. Appropriate means, notshown, such as a fluid actuated cylinder or a screw driven by anappropriate motor, may be provided for displacing the jaw members 32 and34 in unison relatively to the supports l4a-16a such as to provide alimited longitudinal feeding of the electrode wire 24 to compensate forwear of the electrode wire 24. It is obvious that other arrangements maybe utilized for feeding the electrode wire 24 relative to the supportmember 10 and guide members 14-16 to compensate for wear of theelectrode wire.

In operation, the support member 10 is mounted on a portion of theelectro-erosion apparatus, such as the ram of the apparatus, which isdisplaceable relatively to a workpiece, not shown, appropriatelysupported on the bed of the apparatus. The workpiece and the electrodeholder are connected across a power supply of electrical pulses. and thetip of the electrode wire 24 and the workpiece are submerged in adielectric fluid through which the electrical discharges are effected asis well known in the electrical discharge machining art.

In the arrangement of FIGS. l-3. the electrode wire 24 has asubstantially circular section. and the guiding arrangement provided,consisting of two straight edge surfaces 20 and 22 disposed at arelative angle so as to form a V-shaped channel, together with theholding arrangement, consisting of the atmospheric pressure applying theelongated relatively slender electrode wire 24 to the bottom of theV-shaped channel, in combination provides an accurate holding andguiding of the circularly cylindrical electrode wire 24. However, theinvention may be adapted to hold electrode wires of any dimension andshape, as illustrated at FIGS. 4-7.

An arrangement substantially like the arrangement of FIGS. l-3 is shownat FIG. 4, with guide members l4 and 16 provided respectively withstraight edge surfaces 20 and 22. The straight edge surfaces20 and 22form two planar surfaces disposed at an angle of 60 for engaging the twoconsecutive sides of an electrode wire 40 having a cross section in theform of an equilateral triangle. The guide members 14 and 16 aredisposed parallel to each other but are separated by a distance which,combined with the straight edge surfaces 20 and 22 thereon beingdisposed as a bevel at the corner edge of each guide member, provide anappropriate clearance for the edge ofthe wire 40 projecting toward theplanar surface 12 of the support member 10. It is obvious that thearrangement of FIG. 4 can be adapted to diverse sectional shapes ofelectrode wires, such as wires having a triangular, hexagonal, square,or parallelogram cross section, the straight edge surfaces 20 and 22being disposed at an appropriate angle for engaging two fat consecutiveor non-consecutive sides of the electrode wire.

When the electrode wire has a cross section which is rectangular, asshown at FIG. 5 at 42, each of the guide members 14 and 16 is providedwith a planar side 20 and 22 respectively, disposed at a right angle tothe upper planar surface 12 of the support member 10. The electrode wire42 is disposed between the two straight edge surfaces 20 and 22 and ismaintained against the upper surface 12 of the support member byatmospheric pressure, atmospheric air being exhausted through theconduit26 leading into the vacuum manifold 28. A similar arrangement isshown at FIG. 6 for an electrode wire 44 having a square cross section.

Although the embodiments of FIGS. l-6 showing the electrode wire beingmaintained at the bottom of the appropriate guide channel by way of theambient atmospheric pressure, a suction being exerted on the electrodewire at the bottom of the guide channel by way of exhaust conduits 26,are very convenient means for holding an electrode wire in an electrodeholder, it is, however, possible to hold the electrode wire at thebottom of the guide channel by a fluid pressure, either gaseous orliquid, other than atmospheric pressure, exerted on a side of theelectrode wire and tending to urge the electrode wire against the bottomof the guide channel in the electrode holder. Such an arrangement isillustrated at FIG. 7 wherein an electrode wire 46, which, in crosssection, is shaped as a relatively flat member having opposite flatparallel sides connected by curved surfaces, is disposed in a closedchannel 48 formed between the two parallel guide members 14 and 16separated from each other by a constant distance substantiallycorresponding to the thickness of the electrode wire 46. The bottom ofthe channel 48 is defined I top of the channel 48 is closed by a block52-provided placed in communication with the channel 48 by means" of aplurality of conduits 58 so as to introduce the fluid under pressure mtothe channel 48, the fluid leaking around the electrode wire beingexhausted by means of passageways 60 disposed at the bottom of thechannel 48 and communicating with a common manifold 62 connected toambient by conduit 64. In this manner, the electrode wire 46 isconstantly applied in the channel 48 against the guiding groove 50, thegroove 50 forming the equivalent of the straight edge surfaces of thepreviously disclosed embodiments.

Having thus described the invention by way of examples of practicalembodiments thereof, modifications whereof will be apparent to thoseskilled in the art, what is claimed as new is as follows:

I. A holder for supporting and guiding an elongated relatively slenderelectrode in an elec tro-erosion apparatus, said holder comprising anelongated support member, at least one straight edge surfacc on said support member for'defining a lateral support surface of said electrode,and fluid pressure means for urging said electrode against said straightedge surface.

2. The holder of claim 1 comprising a pair of straight edge surfacesangularly disposed one relative to the other. i

3. The holder of claim 1 comprising at least one conduit having an inletdisposed proximate said straight edge surface and an outlet connected tosuction means for exhausting said fluid.

4. The holder of claim 2 comprising at least one conduit having an inletdisposed proximate said straight edge surfaces and an outlet connectedto suction means for exhausting said fluid.

5. The holder of claim 4 wherein said conduit is disposed at the apex ofsaid angularly disposed straight edge surfaces.

6. The holder of claim 3 comprising a plurality of said conduitsdisposed in a row and connected at their outlet to a common suctionmanifold.

7. The holder of claim 4 comprising a plurality of said conduitsdisposed in a row and connected at their outlet to a common suctionmanifold.

8. The holder of claim 5'comprising a plurality of said conduitsdisposed in a row and connected at their outlet to a common suctionmanifold. t

9. The holder of claim 1 comprising an outlet offluid under pressuredisposed on one side of said electrode, and at least one conduit forexhausting said fluid disposed on the other side of said electrodeproximate said straight edge surface.

1. A holder for supporting and guiding an elongated relatively slenderelectrode in an electro-erosion apparatus, said holder comprising anelongated support member, at least one straight edge surface on saidsupport member for defining a lateral support surface of said electrode,and fluid pressure means for urging said electrode against said straightedge surface.
 2. The holder of claim 1 comprising a pair of straightedge surfaces angularly disposed one relative to the other.
 3. Theholder of claim 1 comprising at least one conduit having an inletdisposed proximate said straight edge surFace and an outlet connected tosuction means for exhausting said fluid.
 4. The holder of claim 2comprising at least one conduit having an inlet disposed proximate saidstraight edge surfaces and an outlet connected to suction means forexhausting said fluid.
 5. The holder of claim 4 wherein said conduit isdisposed at the apex of said angularly disposed straight edge surfaces.6. The holder of claim 3 comprising a plurality of said conduitsdisposed in a row and connected at their outlet to a common suctionmanifold.
 7. The holder of claim 4 comprising a plurality of saidconduits disposed in a row and connected at their outlet to a commonsuction manifold.
 8. The holder of claim 5 comprising a plurality ofsaid conduits disposed in a row and connected at their outlet to acommon suction manifold.
 9. The holder of claim 1 comprising an outletof fluid under pressure disposed on one side of said electrode, and atleast one conduit for exhausting said fluid disposed on the other sideof said electrode proximate said straight edge surface.